The present invention relates generally to elevator control systems and, in particular, to a method and an apparatus for the immediate allocation of target calls, also called destination hall calls, within an elevator group.
In a known elevator group control, target calls for travel to desired floors are entered by call registering devices arranged on the floors. These target calls are allocated immediately to the individual elevators of the elevator group by a superordinate target call allocation algorithm supported by a microprocessor. A subordinate costs computation algorithm computes operating costs from elevator related data for each elevator and each target call. The costs are formed as a multipart sum of partial operating costs and correspond to the waiting times and other lost times of passengers. The operating costs of all the elevators are then compared one with the other for each target call and a target call is immediately and definitively allocated to that elevator which displays the smallest corresponding operating costs. The call allocations are indicated on the call registering devices for the potential passengers at the floors.
By such methods as described above, the allocation of target calls to elevators is undertaken in the sense of a special functional behavior to be produced by the elevator group. Such an allocation can be influenced in that one modifies individual, or several, or all terms of the sum of the costs computation in order to improve the traffic development according to special criteria.
In modern controls for elevator groups, the allocation of floor and target calls to the individual elevators takes place in dependence on group-related factors representing the operational status of a elevator group. This reference to the operational status prevailing at the instant of the call allocation permits a better adaptation of the call allocation to the changing traffic incidence and moreover increases the traffic performance.
Thus, a group control for elevators with immediate allocation of target calls is shown in the Swiss Patent Application No. 03-275/88-5, see U.S. Pat. No. 4,991,694 issued Feb. 12, 1991, in which target calls are allocated immediately to a elevator for being served directly after registration. The calls are served on the basis of the effort which is necessary for a call to be served by an elevator and dependent on the instantaneous operational status of the elevator group. Counting as effort is the lost time sum, which is the total time loss that all traffic participants must suffer because of the call being served and which is called operating costs that are computed separately for each elevator. Within the scope of the target call allocation algorithm (ZZA), these operating costs K.sub.NR are computed according to a special costs formula for each elevator and for each target call. The costs are compared call by call in a comparator and the call is subsequently definitively allocated to that elevator which displays the lowest operating costs. For the determination of the operating costs K.sub.NR, the same are split up, according to the traffic participants for whom they arise, into call costs (K.sub.rs ; Kr.sub.rz), passenger costs (K.sub.ps ; K.sub.pz) and waiting costs (K.sub.ws ; K.sub.wz) and represented by the following sum: EQU K.sub.NR =(K.sub.rs +K.sub.rz)+(K.sub.ps +K.sub.pz)+(K.sub.ws +K.sub.wz).
In that case, the call costs (K.sub.rs +K.sub.rz) correspond to the lost times of the traffic participants using the target call concerned, the passenger costs (K.sub.ps +K.sub.pz) correspond to the lost times of the passengers in the car who are not utilizing the target call concerned, and the waiting costs (K.sub.ws +K.sub.wz) correspond to the lost times of the later boarding passengers on the floors who are not utilizing the target call concerned.
The factors, which the individual terms of the sum form, concern time periods and passenger numbers and reflect the respective operational status of the elevator group. As a consequence of these relative status factors, the target call allocation is also relative, namely dependent on and related to the instantaneous operational state of the elevator group at the instant of the call allocation. Although such a target call allocation ascertained according to relative allocation criteria represents an improvement in elevator controls, certain disadvantages are nevertheless entailed by it. These disadvantages result substantially from the circumstance that a target call allocation on the basis of the aforementioned costs formula does not in all cases allocate the target calls in the sense of the demanded functional behavior of modern elevator groups.
A first disadvantage is that ergonomic functional requirements which, for example, concern the habitual accepted behavior of the elevator users, cannot be covered by a lost time minimization. Thus, for example, three "simultaneously" entered identical target calls are distributed over three elevators in the same operational status and parked at the same floor. This is correct from the aspect of the lost time. If all three persons would board the same car, a door opening time, which all three persons would have to endure, would be three times as long as for merely one boarding passenger. On the other hand, in this case, the behavior of the elevator group in minimizing the lost time is incomprehensible or even irritating to the passengers because it contradicts the behavior of a group wherein, typically, only one person enters the target. The pure costs algorithm does not do what this group actually wants to do, namely to "travel as a group". Furthermore, the target floor is blocked for the opposite direction through the simultaneous occupation of the three elevators in the same direction.
A second disadvantage results from the circumstance that, in a target call allocation on the basis of the aforementioned costs formula, the target calls are allocated according to merely a single allocation criterion, namely according to the minimum lost time of all traffic participants. Further function requirements, which should likewise be considered in a target call allocation as allocation criteria for elevator groups, must in that case remain unconsidered. A target call allocation of that kind meets only a portion of the demanded group functions and can therefore not be optimal.
Furthermore, it has proved to be disadvantageous that the target call allocation method according to Swiss Patent Application No. 03-275/88-5, see U.S. Pat. No. 4,991,694 issued Feb. 12, 1991, is based on a closed costs formula which permits no modifications, for example for further allocation criteria What is needed is a target call allocation algorithm with allocation criteria adapting automatically, in kind and number, to kinds of traffic and intensities of traffic, thus a target call allocation which is optimisable for each application.